Eight opiate-experienced, not opiate-dependent volunteers will receive 4 treatments on a partially balanced schedule, with a 6-day interval between treatments. Subjects will be admitted to the GCRC for 72hrs(48hrs after dose administration) The 4 treatments are sublingual administration of 1) buprenorphine 4 mg & naloxone 1 mg, 2) buprenorphine 8 mg and naloxone 2 mg, 3) buprenorphine 16 mg and naloxone 4 mg, 4) buprenorphine alone 16 mg. GCRC facilities are required for sample collection and monitoring.